PAMELA Space Mission
F.S. Cafagna, INFN Barifor the PAMELA Collaboration
F.S. Cafagna, Neutrino Oscillation Workshop, 11 Sept. 2008 2
PAMELA PAMELA CollaborationCollaboration
Moscow St. Petersburg
Russia:
Sweden:KTH, Stockholm
Germany:Siegen
Italy:Bari Florence Frascati TriesteNaples Rome CNR, Florence
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WiZard activities• Astromag/WiZard project (PAMELA precursor) on board of
the Space Station Freedom CANCELED• Balloon-borne experiments: MASS-89,91 TS-93 CAPRICE-
94,97,98 • Space experiments*: NINA-1,2 SILEYE-1,2,3 ALTEA
(*study of low energy nuclei and space radiation environment)
1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007- - - - XASTROMAG
C 94 C 97 C 98TS 93M 89 M 91
SILEYE-1 SILEYE-2 SILEYE-3 ALTEA
NINA-2NINA-1
PAMELAheritage
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PAMELA SciencePAMELA as a Space Observatory @ 1AU
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PAMELA Science
Preliminary
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PAMELA SciencePreliminary
Preliminary
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PAMELA Science
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Why Anti(particle)matter matters?
Earth
F.S. Cafagna, Neutrino Oscillation Workshop, 11 Sept. 2008 9
Why Anti(particle)matter matters?
Earth
F.S. Cafagna, Neutrino Oscillation Workshop, 11 Sept. 2008 10
Why Anti(particle)matter matters?
Earth
F.S. Cafagna, Neutrino Oscillation Workshop, 11 Sept. 2008 11
Why Anti(particle)matter matters?
Earth
F.S. Cafagna, Neutrino Oscillation Workshop, 11 Sept. 2008 12
Why Anti(particle)matter matters?
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PAMELA detectors
Main requirements high-sensitivity antiparticle identification and precise momentum measure
GF: 21.5 cm2 srMass: 470 kgSize: 130x70x70 cm3Power Budget: 360W
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PAMELA detectorsMain requirements high-sensitivity antiparticle identification and precise momentum measure
Spectrometermicrostrip silicon tracking system + permanent magnet
•Magnetic rigidity (R = pc/Ze)•Charge sign•Charge value from dE/dx
+ -
GF: 21.5 cm2 srMass: 470 kgSize: 130x70x70 cm3Power Budget: 360W
Time-Of-Flightplastic scintillators + PMT-Trigger;-Albedo rejection;-Mass identification up to 1 GeV;-Charge identification from dE/dX.
Electromagnetic calorimeterW/Si sampling
(16.3 X0, 0.6λI)• Discrimination e+/ p, pbar/e-(shower topology)
• Direct E measurement for e-
Neutron detectorplastic scintillators + PMT:-High-energy e/h discrimination
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• Antiprotons 80 MeV - 150 GeV
• Positrons 50 MeV – 270 GeV
• Electrons up to 400 GeV
• Protons up to 700 GeV
• Electrons+positrons up to 2 TeV(calorimeter alone)
• Light Nuclei (He/Be/C) up to 200 GeV/n
• AntiNuclei search sensitivity of 3x10-8 in He/He
Design Performance
Simultaneous measurement of many cosmic-ray species New energy range Unprecedented statistics
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PAMELA: the integration
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The Resurs DK-1 spacecraft• Multi-spectral remote sensing of
earth’s surfacenear-real-time high-quality images
• Built by the Space factory TsSKB Progress in Samara (Russia)
• Operational orbit parameters:• inclination ~70o
• altitude ~ 360-600 km (elliptical)
• Active life >3 years • Data transmitted via Very high-
speed Radio Link (VRL)•PAMELA mounted inside a pressurized container•moved from parking to data-taking position few times/year
Mass: 6.7 tonsHeight: 7.4 mSolar array area: 36 m2
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PAMELA: in the satellite & launch
• Launch from Baikonur: June 15th 2006, 0800 UTC.Power On: June 21st 2006, 0300 UTC.Detectors operated as expected after launch
• PAMELA in continuous data-taking mode since commissioning phase ended on July 11th 2006• ~600 days of data taking (~73% live-time) • ~10 TByte of raw data downlinked• >109 triggers recorded and under analysis
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OrbitOrbit CharacteristicsCharacteristics
70ο
610 km
350 kmSAA
•• LowLow--earth elliptical orbitearth elliptical orbit•• 350 350 –– 610 km610 km•• QuasiQuasi--polar (70polar (70oo inclination)inclination)•• Lifetime >3 years (assisted)Lifetime >3 years (assisted)
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Galactic H and He spectraVery high statistics over a wide energy range→ Precise measurement of spectral shape→ Possibility to study time variations and transient phenomena
Statistical errors only
Preliminary
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Geomagnetic cutoff
0.4 to 0.51.0 to 1.51.5 to 2.02 to 4
> 1410 to 147 to 104 to 7
Geomagnetic cutoff (GV/c)
•Up-ward going albedo excluded•SAA excluded
Statistical errors only
Magnetic poles (→ galactic protons)
Secondary Reentrant albedo protons
Magnetic equator
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Interstellar spectrum
July 2006August 2007February 2008
Decreasing
solar activity
Increasing G
CR
flux
Solar modulation
sun-spot number
Ground neutron monitorPAMELA
Statistical errors only
Preliminary
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B/C Ratio
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Antiparticle Selection in the calorimeter
ee-- ee++
p, dp, dpp
Electron
Hadron
Preliminary
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Antiproton:spillover
e- (+ p-bar)
p-bar
p
-1 ← Z → +1
“spillover” p
p (+ e+)
1 GV5 GV
• The main difficulty for the antiproton measurement is the spillover proton bk. At high energy due to the finite deflection resolution of the spectrometer
Deflection:η = 1/R
Preliminary
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MDR depends on:• number and distribution of fitted points along the trajectory• spatial resolution of the single position measurements• magnetic field intensity along the trajectory
High-energy antiproton selection
R < MDR/10
p-bar p
10 GV 50 GV
“spillover” p
MDR = 1/ση(evaluated
event-by-event by the fitting
routine)
Prel
imin
ary
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Antiproton
GV-1
pp pp
β
GV-1
ee-- ee++
pp ppαα
β
GV-1
ee-- ee++
pp pp
β
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Antiproton to Proton RatioAntiproton to Proton Ratio
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Antiproton to Proton RatioAntiproton to Proton Ratio
Preliminary
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Antiproton to Proton RatioAntiproton to Proton Ratio
Preliminary
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Positron selection with calorimeter
(e+)
p (non-int)
p (int)
p-bar (int)
e-
p-bar (non-int)
Z=-1
Z=+1
Rigidity: 20-30 GV
Preliminary
Fraction of charge released along the calorimeter track
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e+
p
p-bar
e-
Positron selection with calorimeterZ=-1
Z=+1
Rigidity: 20-30 GV
Preliminary
Fraction of charge released along the calorimeter track
Constrains on:• Energy momentum
match
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Constrains on:• Energy momentum
match• Shower starting-point• Longitudinal profile
e+
p
e-
Positron selection with calorimeterZ=-1
Z=+1
Rigidity: 20-30 GV
Preliminary
Fraction of charge released along the calorimeter track
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Proton background evaluation
e+
p
e-
p
Rigidity: 6-8 GV
Preliminary
Constrains on:• Energy momentum
match• Shower starting-point• Longitudinal profile
Fraction of charge released along the calorimeter track
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Positron to Electron Fraction
Secondary production Moskalenko & Strong ApJ 493 (1998) 694
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Positron to Electron Fraction
End 2007:~20 000 positrons total
Charge signdependent solarmodulation
Preliminary
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Charge dependent solar modulation
A > 0 Positive particles
A < 0 Clem J. & Evenson 2007
--- Clem 1995--- Bibier 1999 Drift Model
¯
+
¯
+PAMELA
2006 Preliminary
Preliminary
Preliminary
Secondary production Moskalenko& Strong ApJ 493 (1998) 694
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Conclusions
• PAMELA is a permanent cosmic ray space laboratory • Presented preliminary results from ~600 days of data:
• Antiproton charge ratio (~1 GeV ÷100 GeV) • more data to come at lower and higher energies (up to ~150 GeV)
• Positron charge ratio (~400 MeV ÷10 GeV)• more data to come at lower and higher energies (up to ~200 GeV)
• Primary proton and Helium spectra at different geomagnetic cut off latitude and solar activity
• PAMELA is already providing significant experimental results, which will help in understanding and monitorig the flux of CR above the atmosphere
• More exciting results will come in the next future!
PAMELA Space Mission PAMELA CollaborationWiZard activitiesPAMELA SciencePAMELA SciencePAMELA SciencePAMELA ScienceWhy Anti(particle)matter matters?Why Anti(particle)matter matters?Why Anti(particle)matter matters?Why Anti(particle)matter matters?Why Anti(particle)matter matters?PAMELA detectorsPAMELA detectorsDesign PerformancePAMELA: the integrationThe Resurs DK-1 spacecraftPAMELA: in the satellite & launchOrbit CharacteristicsGalactic H and He spectraGeomagnetic cutoffSolar modulationB/C RatioAntiparticle Selection in the calorimeterAntiproton:spilloverHigh-energy antiproton selectionAntiprotonAntiproton to Proton RatioAntiproton to Proton RatioAntiproton to Proton RatioPositron selection with calorimeterPositron selection with calorimeterPositron selection with calorimeterProton background evaluationPositron to Electron FractionPositron to Electron FractionCharge dependent solar modulationConclusions